Approaches used to effect selective reaction at one of two or more similar sites in a molecule are reviewed. The nature of the problem is defined and the strategic advantage to be gained through the use of symmetrical intermediates is outlined early and re-emphasised throughout the discussion with specific examples of multistage syntheses of important products. The various tactics used to effect site selectivity in a late synthetic step are described in a logical sequence and presented in a form aimed to help in the design of syntheses of unsymmetric products from symmetric intermediates.